It
is widely believed by Thais, that theirs was one of the
countries that Asoka sent Buddhist missionaries
to in the 3rd century BC. While this is quite possible,
there is at present no evidence to support this belief.
However by the 6th century AD Buddhism was well established
in south and central areas of what is now Thailand. Later
Mahayana and Tantra together with Hinduism
became the prominent religions. But in the 13th and 14th
centuries monks from Sri
Lanka succeeded in establishing Theravada
Buddhism and it has remained the state religion ever since.

Never
having been conquered by the colonial powers, Thailand
was never subjected to assaults by Christian missionaries
or imposed Western influence, and today some 94% of Thais
call themselves Buddhists. In the 19th century King Mongkut,
himself a former monk, conducted a campaign to reform
and modernise the monkhood, a movement that has continued
in the present century under the inspiration of several
great ascetic monks from the north-east of the country.
The Western disciples of one of these monks, Ajhan Cha,
have successfully founded thriving monasteries in the
U.K., Australia, New Zealand and several other countries.

D.Nivat,
A History of Buddhism in Siam, Bangkok, 1965;
K.E.Wells Thai Buddhism- Its Rites and Activities,
Bangkok, 1975;
K.Kusalasaya, Buddhism in Thailand- Its Past and Present,
Kandy, 1983.